Faster Planetary Exploration

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The mission was launched on an Ariane 5 rocket on 20 October 2018, with Mercury orbit insertion planned for November 2026, after a flyby of Earth, two flybys of Venus, and six flybys of Mercury. The total cost of the mission was estimated in 2017 as US$2 billion. When I read this, I was really disappointed. It takes almost a decade to send two small satellites to Mercury and cost more than two billion.

I had previously proposed a LEO assembled planetary rocket. Developing such a system would dramatically reduce the cost and the duration to reach the planets. Development only requires modified payload section for Falcon family of rockets. These payload stages would serve as the stages of an interplanetary rocket. Only two launches would be enough to form a rocket to deploy BepiColombo to Mercury with a direct trajectory.

Once the rocket stages are connected in LEO, the interplanetary rocket's first stage would be fired to accelerate the spaceship. The rocket would utilize highly efficient ion thrusters. These thrusters would continuously accelerate the rocket until it reaches the escape velocity. A rocket orbiting the earth would experience no gravity, therefore even the small thrust generated by the ion thruster would allow it to reach the escape velocity over time. This time would be several days not a decade like in the above example.

The objective of the interplanetary rocket’s first stage is to put the upper stages into the trans planetary trajectory. Once this objective is reached, first stage would be ejected. The second stage of the rocket which also utilize an ion thruster would maneuver the rocket on its path to the target planet. As the rocket approaches the target planet, the second stage would be used to slow down the rocket. For an inner planet mission, the sun rays would be used to generate more electric power and heat the ionized gas which lead to higher thrust. The problem with BepiColombo was that it didn’t have a stage to decelerate the satellites to allow orbital injection. Instead, gravity assist was utilized which took almost a decade to achieve the required slowing down.

As a conclusion, the planetary missions that have decelerating stage do not require giant rockets. Current Falcon rockets allow LEO assembling a rocket. Just invent a LEO assembled interplanetary rocket for a much faster Solar exploration.